text: Earth constantly absorbs energy from sunlight and emits thermal radiation as infrared light.
  In the long run, Earth radiates the same amount of energy per second as it absorbs, because the amount of thermal radiation emitted depends upon temperature: If Earth absorbs more energy per second than it radiates, Earth heats up and the thermal radiation will increase, until balance is restored; if Earth absorbs less energy than it radiates, it cools down and the thermal radiation will decrease, again until balance is restored.
  Atmospheric CO absorbs some of the energy radiated by the ground, but it emits itself thermal radiation: For example, in some wavelengths the atmosphere is totally opaque due to absorption by CO; at these wavelengths, looking at Earth from outer space one would not see the ground, but the atmospheric CO, and hence its thermal radiation—rather than the grounds thermal radiation. Had the atmosphere been at the same temperature as the ground, this would not change Earths energy budget; but since the radiation is emitted from atmosphere layers that are cooler than the ground, less radiation is emitted.
  As CO content of the atmosphere increases due to human activity, this process intensifies, and the total radiation emitted by Earth diminishes; therefore, Earth heats up until the balance is restored.